From 95c8d27b0bfdea330a62a18825dea3691b4affe2 Mon Sep 17 00:00:00 2001 From: David Shah Date: Tue, 16 Jul 2019 16:46:41 +0100 Subject: xilinx: Treat DSP48E1 as 24x17 unsigned for now (actual behaviour is 25x18 signed) Signed-off-by: David Shah --- techlibs/xilinx/synth_xilinx.cc | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'techlibs/xilinx/synth_xilinx.cc') diff --git a/techlibs/xilinx/synth_xilinx.cc b/techlibs/xilinx/synth_xilinx.cc index 01e75b50e..5bfbd1583 100644 --- a/techlibs/xilinx/synth_xilinx.cc +++ b/techlibs/xilinx/synth_xilinx.cc @@ -284,8 +284,12 @@ struct SynthXilinxPass : public ScriptPass run("techmap -map +/cmp2lut.v -D LUT_WIDTH=6"); + // The actual behaviour of the Xilinx DSP is a signed 25x18 multiply + // Due to current limitations of mul2dsp, we are actually mapping as a 24x17 + // unsigned multiply with MSBs set to 1'b0 + if (!nodsp || help_mode) - run("techmap -map +/mul2dsp.v -D DSP_A_MAXWIDTH=25 -D DSP_B_MAXWIDTH=18 -D DSP_NAME=$__MUL25X18"); + run("techmap -map +/mul2dsp.v -D DSP_A_MAXWIDTH=24 -D DSP_B_MAXWIDTH=17 -D DSP_NAME=$__MUL25X18"); run("alumacc"); run("share"); -- cgit v1.2.3